Plaid sync domain improvements (#2267)

Breaks our Plaid sync process out into more manageable classes. Notably, this moves the sync process to a distinct, 2-step flow:

1. Import stage - we first make API calls and import Plaid data to "mirror" tables
2. Processing stage - read the raw data, apply business rules, build internal domain models and sync balances

This provides several benefits:

- Plaid syncs can now be "replayed" without fetching API data again
- Mirror tables provide better audit and debugging capabilities
- Eliminates the "all or nothing" sync behavior that is currently in place, which is brittle

test/models/plaid_entry/processor_test.rb

@@ -0,0 +1,91 @@
+require "test_helper"
+
+class PlaidEntry::ProcessorTest < ActiveSupport::TestCase
+  setup do
+    @plaid_account = plaid_accounts(:one)
+    @category_matcher = mock("PlaidAccount::Transactions::CategoryMatcher")
+  end
+
+  test "creates new entry transaction" do
+    plaid_transaction = {
+      "transaction_id" => "123",
+      "merchant_name" => "Amazon", # this is used for merchant and entry name
+      "amount" => 100,
+      "date" => Date.current,
+      "iso_currency_code" => "USD",
+      "personal_finance_category" => {
+        "detailed" => "Food"
+      },
+      "merchant_entity_id" => "123"
+    }
+
+    @category_matcher.expects(:match).with("Food").returns(categories(:food_and_drink))
+
+    processor = PlaidEntry::Processor.new(
+      plaid_transaction,
+      plaid_account: @plaid_account,
+      category_matcher: @category_matcher
+    )
+
+    assert_difference [ "Entry.count", "Transaction.count", "ProviderMerchant.count" ], 1 do
+      processor.process
+    end
+
+    entry = Entry.order(created_at: :desc).first
+
+    assert_equal 100, entry.amount
+    assert_equal "USD", entry.currency
+    assert_equal Date.current, entry.date
+    assert_equal "Amazon", entry.name
+    assert_equal categories(:food_and_drink).id, entry.transaction.category_id
+
+    provider_merchant = ProviderMerchant.order(created_at: :desc).first
+
+    assert_equal "Amazon", provider_merchant.name
+  end
+
+  test "updates existing entry transaction" do
+    existing_plaid_id = "existing_plaid_id"
+
+    plaid_transaction = {
+      "transaction_id" => existing_plaid_id,
+      "merchant_name" => "Amazon", # this is used for merchant and entry name
+      "amount" => 200, # Changed amount will be updated
+      "date" => 1.day.ago.to_date, # Changed date will be updated
+      "iso_currency_code" => "USD",
+      "personal_finance_category" => {
+        "detailed" => "Food"
+      }
+    }
+
+    @category_matcher.expects(:match).with("Food").returns(categories(:food_and_drink))
+
+    # Create an existing entry
+    @plaid_account.account.entries.create!(
+      plaid_id: existing_plaid_id,
+      amount: 100,
+      currency: "USD",
+      date: Date.current,
+      name: "Amazon",
+      entryable: Transaction.new
+    )
+
+    processor = PlaidEntry::Processor.new(
+      plaid_transaction,
+      plaid_account: @plaid_account,
+      category_matcher: @category_matcher
+    )
+
+    assert_no_difference [ "Entry.count", "Transaction.count", "ProviderMerchant.count" ] do
+      processor.process
+    end
+
+    entry = Entry.order(created_at: :desc).first
+
+    assert_equal 200, entry.amount
+    assert_equal "USD", entry.currency
+    assert_equal 1.day.ago.to_date, entry.date
+    assert_equal "Amazon", entry.name
+    assert_equal categories(:food_and_drink).id, entry.transaction.category_id
+  end
+end